set specific bone as child of object
If you want the IK-Handle to stay in the same position as the pencil, simply use a Bone Constraint on the IK-Handle. Select the IK-Handle in Pose Mode and add the Copy Location Constraint from the Bone Constraint Menu (not the regular Object Constraints, see screenshot). Choose the pencil as a target, the bone will then follow the pencils origin. 



If that origin is not where you would like, simply parent an Empty to the pencil in the place you want the hand to grip it and target the Bone Constraint to that Empty.